Congenital Malformations Registry - Summary Report

Section V: Comparison of Selected Malformation Prevalence with Other Birth Defects Registries

Introduction to Table

The CMR relies on reports from hospitals and physicians for case ascertainment. Underreporting is an obvious concern, and the CMR over the years has developed methods to improve case ascertainment and monitor hospital reporting (Appendix 3). In this section, CMR live birth prevalences are compared with the national prevalence estimates for 21 selected defects developed by the Centers for Disease Control and Prevention (CDC) and the National Birth Defects Prevention Network (NBDPN).1 The 21 defects were selected as they are generally diagnosed soon after birth and the accuracy of diagnosis should be similar across sites1.These estimates were based on 11 registries which use active case-finding. Active case-finding uses data collection specialists who go to hospitals to identify and abstract records of children with malformations. The active case-finding systems were chosen as they have similar methodology and prevalence estimates are usually higher in systems using active case finding, although variation was observed even among the 11 active case finding systems (See Figure 1 in Canfield1).

As can be seen from Table 1, the CMR prevalences are equal to or higher than the lower boundary of the actual range of the 11 registries for 16 of the 21 defects (bold prevalences) and five of the defects are equal to or higher than the lower 95 percent confidence interval (CI) (boxed prevalences). The prevalences are generally higher for New York State excluding New York City than for New York City (18 defect prevalences are equal to or higher than the lower boundary of the actual range of the 11 registries compared to 12 for New York City).

The interpretation of differences among registry prevalences is difficult. The lower prevalences of the CMR for neural tube defects (NTD), anophthalmia/microphthalmia and trisomy 18 is most likely due to the lack of reports on terminations as termination rates for these conditions are high. The lower prevalence for cleft lip with/without cleft palate is more difficult to explain. There has been little variation in the prevalence since 1983 and it is an easily identified condition. There is also a wide variation within New York State itself from 5.4 in New York City to 13.0 in another region. The lower rates in limb reduction are also more difficult to explain as these are also easily recognizable defects. We have noted that the rate has been declining over several years, especially for lower limbs and plan to examine defect trends in a future report.

None of the 11 registries had all 21 defect prevalences fall within the 95 percent confidence intervals. Several registries would have the highest prevalence for one defect and the lowest prevalence for others. Variation among the registries in the rates of specific defects could reflect demographic differences in the populations as there are racial and ethnic differences in the rates of specific birth defects1. The prevalence of Down syndrome, trisomy 18 and trisomy 13 is highly dependent upon the maternal age distribution, age-specific pregnancy rates and women's use of prenatal diagnosis and pregnancy termination. The lower live birth prevalence rates of these chromosomal abnormalities in the CMR may be partially attributable to one or more of these factors. However, the source(s) of much of the variation is unclear and there may be true geographic differences. A comparison of birth defect prevalences between the Metropolitan Atlanta Congenital Defects Program (MACDP) and California Birth Defects Monitoring program (CBDMP) for the years 1983-1988 that adjusted for race, sex and maternal age showed regional differences in arm, hand and limb reduction defects 2.

CMR staff will continue their efforts to improve reporting (See Appendix 3) and will track our progress using the NBDPN national prevalence estimates.

Section V - Table 1
Prevalence* of Selected Major Birth Defects in New York State (Birth years: 2003-2005)
Brith Defect Category New York City Upstate NY New York State NBDPN
1999-2001
95% CI
Range
Central nervous system defects
Anencephalus 0.3 0.5 0.4 2.5 2.3-2.7
Spina bifida without anencephalus 1.6 2.2 1.9 3.7 3.4-3.9
Encephalocele 0.4 0.6 0.5 0.9 0.8-1.0
Eye defects
Anophthalmia/ microphthalmia 0.6 0.9 0.8 2.1 1.9-2.3
Cardiovascular defects
Common truncus 1.0,* 0.4 0.7,* 0.8 0.7-0.9
Transposition of great arteries 3.6 4.7,* 4.2 4.7 4.5-5.0
Tetralogy of Fallot 4.8,* 4.9,* 4.9,* 3.9 3.8-4.2
Endocardial cushion defect 2.6 3.1 2.8 4.4 4.1-4.6
Hypoplastic left heart syndrome 2.1 2.8,* 2.5,* 2.4 2.2-2.6
Orofacial defects
Cleft palate without cleft lip 4.2 6.5,* 5.4 6.4 6.1-6.7
Cleft lip with and without cleft palate 5.4 8.4 7.0 10.5 10.1-10.9
Gastrointestinal defects
Esophageal atresia/ tracheosophageal fistula 2.7,* 2.0 2.4,* 2.4 2.2-2.6
Rectal and large intestinal atresia/stenosis 4.4 4.7,* 4.6,* 4.8 4.5-5.1
Musculoskeletal defects
Reduction deformity, upper limbs 1.4 2.1 1.8 3.8 3.5-4.0
Reduction deformity, lower limbs 0.7 1.0 0.9 1.9 1.7-2.1
Gastroschisis 1.4 2.5 2.0 3.7 3.5-4.0
Omphalocele 1.1 1.4 1.3 2.1 1.9-2.3
Diaphragmatic hernia 1.8 2.5 2.2 2.9 2.7-3.1
Chromosomal defects
Trisomy 13 0.9 0.9 0.9 1.3 1.2-1.5
Down syndrome(trisomy 21) 11.0 13.6,* 12.4 13.7 13.2-14.1
Trisomy 18 0.9 1.1 1.0 2.4 2.2-2.6
a - Prevalence (number of defects per 10,000 live births)
prevalences are within the range of the 11 active registries
†,* prevalences are equal to or greater than the lower limit of the 95% CI range

References

  1. Canfield MA, Honein MA, Yuskiv N et al. National Estimates and Race/Ethnic Specific Variation of Selected Birth Defects in the United States, 1999-2001. Birth Defects Research(Part A) 2006;76:747-756.
  2. Schulman J, Edmonds LD, McClern AB, et al. Surveillance for and comparison of birth defect prevelences in two geographic areas - United States 1983-1988. In: CDC Surveillance Summaries; March 19, 1993. Morbidity and Mortality Weekly Report 1993; 42(No. SS-1):1-7.